1. Field of the Invention
The present invention relates to a paper web running tension controller for adjusting the tension of a paper web fed from a paper feed unit to a printing unit in a rotary press by displacement of a dancer roller and a rotation control of an in-feed roller independently driven, and particularly to a controller of running tension of paper web for rotary press capable of rapidly and smoothly absorbing tension variations and stabilizing the tension.
2. Description of the Related Art
In the art of a running tension controller in a path in which the paper web that is drawn out from a paper feed unit of a rotary press is fed to a printing unit, a conventional system is disclosed in Japanese Patent No. 3035301.
The art described in Japanese Patent No. 3035301 includes an in-feed roller for feeding a paper web toward the printing unit from the paper feed unit, a dancer roller for absorbing looseness of the paper web fed into the printing unit, pressing means for pressing the dancer roller against the paper web, position detection means for detecting the position of the dancer roller, an independent drive motor which is separated from the other drive systems and drives the in-feed roller, and control means for controlling the independent drive motor, so that during a normal operation, a ratio of the speed of the in-feed roller to the running speed of the paper web is set based on the output of the position detection means in order that the position of the dancer roller is kept in a specified area, and based thereon the independent drive motor is controlled.
The dancer roller always reciprocates, and when the position of the dancer roller is deviated to a high tension side, that is, in the direction in which the path becomes shorter, from the specified area, the speed of the in-feed roller is increased a little. By the increase in the speed, the position of the dancer roller is returned into the specified area, and when the dancer roller moves to pass there and is deviated to a low tension side, that is, in the direction in which the path becomes longer, from the specified area, the speed of the in-feed roller is decreased a little. By the decrease in the speed, the position of the dancer roller is returned into the specified area, and the dancer roller repeats reciprocation so as to move until it is further deviated to the high tension side, while the in-feed roller alternatively increases and decreases the speed.
At the time of starting operation, during a specified period until the position of the dancer roller enters the specified area, the speed ratio is set at a specified speed ratio based on the stop position of the dancer roller before the operation is started and based upon this, the independent drive motor is controlled.
When the dancer roller, which starts to move based on the specified ratio for the specified period at the start of operation, moves into the specified area which is set within a range where it can move, the speed ratio is set at the ratio similarly set at the time of the normal operation so that the dancer roller is kept within the specified area, and the dancer roller always reciprocates within the specified area like a pendulum.
At the time of the normal operation, the control means sets the speed ratio of the in-feed roller that differs a little relative to the running speed of the paper web based on the output of the position detection means so that the position of the dancer roller is kept within the specified area while always reciprocating, and performs the control based on this speed ratio so that the independent drive motor alternatively repeals an increase and a decrease of the speed. During the specified period at the start of the operation, the speed ratio is set at a predetermined specified speed ratio, and the independent drive motor is controlled based on the specified speed ratio.
Consequently, after the specified period at the start of the operation elapses, when a disturbance that causes the tension of the paper web to reduce works in succession while, for example, the dancer roller is moving to the low tension side, the position of the dancer roller is temporarily displaced to the low tension side to a large extent from the specified area. In such a case, the speed ratio of the in-feed roller also remains to be the speed ratio at the time of the aforementioned normal operation, and the rotation of the in-feed roller is controlled to be slightly decelerated. When the displaced dancer roller takes time to slowly return to the specified area, if the similar tension variations subsequently occur, the dancer roller is displaced further to the low tension side to absorb the tension variations and tries to absorb the tension variations, and therefore the dancer roller is deviated to a large extent from the aforementioned specified area to eliminate looseness of, for example, the paper web, which not only makes it difficult for the dancer roller to return to the specified area, but also causes the case in which it cannot absorb the tension variations and results in a lack of stability of tension, whereby there arises the possibility that a misregistration of printing is caused especially in the case of multicolor printing and the printing quality is impaired.
An object of the present invention is to provide a controller of running tension of paper web for rotary press, which drives a printing cylinder and an in-feed roller having separate drive means according to a common operation speed command, makes a difference of peripheral speeds of the printing cylinder and the in-feed roller larger as a displacement amount from a reference position provided in a displacement range of a dancer roller is larger to make tension variations caused by disturbances be surely absorbed, is capable of making the displacement amount small by moving the dancer roller quickly to the reference position, smoothly and gradually decreasing the difference of the peripheral speed of the in-feed roller relative to that of the printing cylinder so that the peripheral speeds thereof become the same when the dancer roller reaches the reference position, whereby the dancer roller does not always reciprocate, quickly returns to the reference position from the position with a large displacement amount, always keeps absorption ability of the tension variations high, and by extension, stable tension is maintained, eliminates misregistration, and maintains and improves printing quality.
Another object of the present invention is to provide a tension control processing unit suitable for controlling rotation of the in-feed roller.
Still another object of the present invention is to provide a paper web running controller for a rotary press capable of obtaining a printing paper surface without misregistration by stabilizing tension by increasing the ratio of the difference of the peripheral speed of the in-feed roller relative to the printing cylinder more than the case in which the operation is at a high speed side exceeding the aforementioned predetermined operation speed when the operation of the rotary press is at a lower speed side within a range not higher than the predetermined operation speed previously specified, the dancer roller displaced due to the aforementioned disturbances is returned to the reference position more quickly from the displacement position so that ability to absorb tension variations is always able to be kept high as in the case of the aforementioned high speed side.
In a disclosed embodiment, a controller of running tension of paper web for rotary press is constituted to have an in-feed roller which is placed to form a running path of paper web drawn out of paper roll to reach the printing cylinder and is rotationally driven by independent drive means; a dancer roller device having the dancer roller, which is placed to form the running path of the paper web from an area after the in-feed roller to an area where the paper web reaches the printing cylinder and is provided to be displaceable to absorb variations of running tension of the paper web, and provided with displacement detection means for detecting a displacement amount of the dancer roller; and a tension control processing unit for controlling a rotational speed of the aforementioned in-feed roller by controlling an operation of the aforementioned independent drive means based on the displacement amount of the dancer roller detected in the displacement detection means and the operation speed command, so that a peripheral speed of the in-feed roller becomes the same as a peripheral speed of the printing cylinder when the dancer roller is at a reference position specified in a displacement range thereof, the peripheral speed of the in-feed roller becomes lower than the peripheral speed of the printing cylinder when the dancer roller is displaced to a position at which the running path of the paper web is made longer than at the reference position, and the peripheral speed of the in-feed roller becomes higher than the peripheral speed of the printing cylinder when the dancer roller is displaced to a position at which the running path of the paper web is made shorter than at the reference position, and by controlling the operation of the aforementioned independent drive means so that as the displacement amount of the dancer roller from the reference position becomes larger, the difference of the peripheral speeds of the printing cylinder and the in-feed roller becomes larger.